Optimal Pony Bottle Size for Failure at 100ft?

[johndiver999]

It comes from technical diving. If you have a problem, taking a couple of minutes to handle the problem at depth is arguably a more reasoned solution than trying to make an ascent, under stress, while trying to do what amounts to a gas switch.

Thinking about it from a rec perspective, if you run completely OOG, you spend a second doing a switch and getting yourself under control before you start the ascent. Now you have gas, and you can take your time to manage the ascent.... that's scenario one. In your scenario, you have to switch gasses and manage your ascent simultaneously under stress. That's more likely to end up in an uncontrolled ascent.

IMO, if you are taking the time to ensure that you've got sufficient gas for the ascent, you're probably going to pay sufficient attention to your gas generally, so you will likely avoid getting task-loaded enough to run OOG. I'm not saying that's impossible, but it is less likely to occur. There are a range of other possibilities that might make you want to switch to your pony though. Being low on gas and some random dude shows up OOG, maybe a free-flowing regulator, maybe something else involving a buddy where you just can't or don't want to make like a Polaris Missle.

This is a silly perspective. The whole idea is to use the pony as a bail out bottle. It is simple to switch, it is simple to press the up button. It should take no time at all. What is there to contemplate at 100 feet as you suck on a small bottle, that you MAY or MAY NOT know how much air is contained within?

Many people, like myself, opt for a small button gage on the pony. They can not read it underwater. They really don't know how much air leaked during the dive and if they are stupid, they might not even double checked it was on before the dive. You have a complete loss of gas at 100 ft and you are alone, get the hell out of dodge! Once you are relaxed, not swimming, and ascending at an optimal rate, you should be able to calm down and concentrate on regulating your buoyancy. There is no polaris missile.

If you really can't do that, then you shouldn't be diving at 100 feet. Do you think it is CALMING to sit on the bottom of the ocean, all alone, with no other option and suck on a pony bottle? Not me, I want to be moving and know I have a slight cushion of expanding air in my BC.

 

[VikingDives]

This is a silly perspective. The whole idea is to use the pony as a bail out bottle. It is simple to switch, it is simple to press the up button. It should take no time at all. What is there to contemplate at 100 feet as you suck on a small bottle, that you MAY or MAY NOT know how much air is contained within?

Many people, like myself, opt for a small button gage on the pony. They can not read it underwater. They really don't know how much air leaked during the dive and if they are stupid, they might not even double checked it was on before the dive. You have a complete loss of gas at 100 ft and you are alone, get the hell out of dodge! Once you are relaxed, not swimming, and ascending at an optimal rate, you should be able to calm down and concentrate on regulating your buoyancy. There is no polaris missile.

If you really can't do that, then you shouldn't be diving at 100 feet. Do you think it is CALMING to sit on the bottom of the ocean, all alone, with no other option and suck on a pony bottle? Not me, I want to be moving and know I have a slight cushion of expanding air in my BC.

You do you. I was answering a question on why people plan that way.

Having a potentially empty pony bottle and running out of gas might sound like a reasonable plan to you, but I think a lot of folks are going to find your ideas silly.

 

[scubadada]

Many of the contentious issues regarding the use of a pony for redundant gas supply have been discussed many times before. It comes down to personal preferences.

I dive a slung pony with a SPG on a short hose and the valve on. The pony is always right in front of me, I could easily see any leak, I know exactly how much gas is in it, and it is immediately ready for use.

I chose to use a 19 cu ft pony. The deepest I would dive solo is around 130 feet, nearly all my dives are shallower than that but are not uncommonly around 100 ft. My conservative calculation for gas requirement is a minute at depth, a normal ascent, and a 3 min safety stop, all at twice my average RMV

One minute at 130 ft: 1 x (130/33 + 1) x 0.72 = 3.6 cu ft
Normal ascent: 4.33 x (65/33 + 1) x 0.72 = 9.3 cu ft
3 min safety stop: 3 x (15/33 + 1) x 0.72 = 3.1 cu ft

Total gas requirement: 16 cu ft, that leaves me with about 3 cu ft/475 psi in my pony. I keep my pony up to pressure with a transfill hose. My calculation is conservative. I would not intend on spending time on the bottom. For a no stop dive, the safety stop is optional. If push came to shove, I would increase my ascent rate.

 

[grantmac]

On a no-stop dive I would shorten a safety stop before increasing ascent rate if I had any gas left at all.

 

[johndiver999]

On a no-stop dive I would shorten a safety stop before increasing ascent rate if I had any gas left at all.

Take a moment to think about how you would accomplish this sequence of actions.

 

[grantmac]

Take a moment to think about how you would accomplish this sequence of actions.

I'm not going to increase rate of ascent for anything except complete lack of breathable gas on a no-stop dive.
AGE is much more dangerous than getting bent.

 

[lowwall]

I'm not going to increase rate of ascent for anything except complete lack of breathable gas on a no-stop dive.
AGE is much more dangerous than getting bent.

Keep your airway open. Ascent rate shouldn't make a difference.

 

[johndiver999]

A moderately accelerated ascent rate , especially when deep does is not an issue for age,

 

[grantmac]

I have done quite a lot of NDL diving with fast ascent rates in the past with any forms of safety stop (military) and for me the higher ascent rate has greater risks than the lack of a stop.

 

[rjack321]

You GUE guys need to come to terms that people are going to continue to use pony bottles for redundancy. It is a perfectly valid configuration for recreational diving. Just let it go.

Yet the seem to create almost as many problems as they solve. Maybe they aren't as valid as they appear.